EP0163078B1 - Delivery valve - Google Patents

Delivery valve Download PDF

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Publication number
EP0163078B1
EP0163078B1 EP85104323A EP85104323A EP0163078B1 EP 0163078 B1 EP0163078 B1 EP 0163078B1 EP 85104323 A EP85104323 A EP 85104323A EP 85104323 A EP85104323 A EP 85104323A EP 0163078 B1 EP0163078 B1 EP 0163078B1
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EP
European Patent Office
Prior art keywords
valve
delivery
closing member
injection
pressure
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP85104323A
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German (de)
French (fr)
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EP0163078A1 (en
Inventor
Peter Dipl.-Math. Wannenwetsch
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Robert Bosch GmbH
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Robert Bosch GmbH
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Publication date
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Publication of EP0163078A1 publication Critical patent/EP0163078A1/en
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Publication of EP0163078B1 publication Critical patent/EP0163078B1/en
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M55/00—Fuel-injection apparatus characterised by their fuel conduits or their venting means; Arrangements of conduits between fuel tank and pump F02M37/00
    • F02M55/02—Conduits between injection pumps and injectors, e.g. conduits between pump and common-rail or conduits between common-rail and injectors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M59/00—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps
    • F02M59/44—Details, components parts, or accessories not provided for in, or of interest apart from, the apparatus of groups F02M59/02 - F02M59/42; Pumps having transducers, e.g. to measure displacement of pump rack or piston
    • F02M59/46—Valves
    • F02M59/462—Delivery valves
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/7722—Line condition change responsive valves
    • Y10T137/7771—Bi-directional flow valves
    • Y10T137/7772—One head and seat carried by head of another
    • Y10T137/7774—Supporting valve spring carried by supporting valve

Definitions

  • the invention is based on a pressure valve according to the preamble of the main claim.
  • a pressure valve known from CH-PS-394 710
  • the so-called dripping or re-injection of fuel after the effective delivery stroke of the injection pump piston is to be prevented by providing a return suction collar on the pressure valve in combination with a relief throttle, optionally controlled by a pressure-maintaining valve .
  • pressure waves would occur in the fuel supply line between the pressure valve and the injection valve, which would reciprocate between the injection valve and the pressure valve.
  • the returning waves reflected from the pressure valve to the injection valve can subsequently open it, so that fuel leaks occur with the known disadvantages.
  • the known configuration has only the purpose of preventing the injection or dripping, namely in a wide range of the injection quantity control per injection stroke.
  • the relief throttle which is not controlled by a pressure control valve, has the effect that the residual pressure in the fuel delivery line changes greatly with the speed.
  • the delivery line between the pressure valve and the injection valve is relieved in the same way as with large injection quantities.
  • a more or less large swallowing volume is effective, which has to be filled up by the pump piston delivery until the injection pressure at the injection valve is reached.
  • this disadvantageously leads to noticeable quantity spreads due to the different residual pressures, which have a disadvantageous effect on the running behavior of the internal combustion engine.
  • part of the useful stroke of the pump piston is lost.
  • a cylinder fitted into the passage channel of the valve body is provided as the guide part of the pressure valve closing element.
  • the fuel delivery with the pressure valve open then takes place via the axial relief channel upstream of the throttle and a transverse channel which connects the relief channel to an annular groove separating the suction collar from the guide part.
  • relief of the spring chamber is only possible via the relief channel which extends coaxially through the entire valve closing member.
  • the throttle connection on the valve closing member of the pressure valve is then intended to prevent the valve closing member from lifting during ignition fuel injection by the amount which corresponds to the relief volume without the throttle. This is to prevent the fuel delivery line from being relieved by the full amount of the relief volume made available by the relief association at the end of the spray. This relief would lead to an unsatisfactory operating result.
  • the throttle connection is intended to switch off the discharge completely in the operating range in which ignition fuel is to be injected, in that the amount of ignition fuel flows past the relief collar via the throttle connection without any noticeable pressure drops. In the case of pure liquid power operation, on the other hand, the relief provided by the return suction collar should take full effect.
  • a pressure valve is also known from FR-A-1 050 441, in which a check valve is integrated.
  • this pressure valve has no closing element which has a continuous relief channel.
  • the check valve of this known pressure valve closes a channel leading to the injection side and is connected on the valve spring side to a pressure chamber which is enclosed between a head and a suction collar of the pressure valve closing member in the through channel of the pressure valve.
  • the head in this known pressure valve closing member has a cylindrical part which, in the closed state, lies within a cylindrical bore which is enlarged compared to the diameter of the valve seat.
  • the cylindrical part has an annular gap with the cylindrical bore or it is tightly fitted.
  • the delivery rate is increased briefly at the start of delivery in such a way that a pre-injection occurs, which is terminated when the cylindrical part of the pressure valve closing member emerges from the cylindrical bore and the remaining part has to be filled up to the prevailing pressure level.
  • the check valve has the task that the opening movement is not impeded even when there is sufficient play between the cylindrical part and the cylindrical bore. When the valve is opened, the check valve can be used to equalize the pressure in the enclosed space.
  • this pressure valve and the other proposed solutions according to FR-A-1 050 441 serve the purpose of achieving a damped closing movement of the valve closing element, in order to reduce pressure waves in the injection line after the end of delivery, in addition to the volume relief by means of a suction collar, instead of as in the case of the Pressure valve according to CH-A-394 710 to use a check valve, serving as a constant pressure valve.
  • the pressure in the delivery line cannot generally be limited to a maximum value.
  • the actual stroke of the valve corresponds in all cases in which the damping device is relieved to the injection valve to the delivered fuel injection quantity.
  • the delivery line is relieved of relatively high loads with small injection quantities analogous to the relief for larger injection quantities.
  • the pressure valve according to the invention with the characterizing features of the main claim has the advantage that the pressure in the delivery line is generally limited to a maximum value by the check valve, which is less than the opening pressure of the fuel injector, so that no post-injection can occur.
  • the configuration of the return suction collar ensures that, with small injection quantities or with a low delivery rate of the fuel delivered from the pump work chamber to the injection valve, the fuel can flow over the throttle connection without the valve closing member of the pressure valve being lifted substantially from its seat.
  • the relief stroke or the effect of the relief collar when the pressure valve is closed is then correspondingly small, so that a relatively high residual pressure remains in the delivery line. So that this residual pressure does not exceed the opening pressure of the injection valves, the effect of the check valve is essential here.
  • the throttling effect of the throttle connection increases in such a way that fuel quantities influencing the movement of the closing element of the pressure valve hardly overflow here.
  • the return suction collar thus comes into full effect in such a way that the effect of the check valve is no longer of fundamental importance for maintaining a residual pressure below the nozzle opening pressure.
  • the pump piston delivers a uniformly long delivery phase. This is particularly important when the internal combustion engine is operated with a so-called quiet running device, as already mentioned.
  • the fuel delivery should also be used with the effective delivery stroke of the pump piston. This also applies in particular to the critical range of idling and the low load and is achieved by the high residual pressure that can be achieved with the device according to the invention. A useful stroke loss, which is particularly disadvantageous for idle operation, is also avoided.
  • the requirements can be met in all operating areas of an internal combustion engine, which is operated in particular with a silent running device, and the working capacity in relation to the useful stroke of the fuel supply device can be optimally utilized.
  • the residual pressure in the delivery line which can be controlled with the pressure valve according to the invention, can be used to influence the duration of the spray at a given cross section of the injection nozzle.
  • the figure shows a longitudinal section through a pressure valve 1, which is screwed into the housing 2 of a fuel injection pump, not shown, which is constructed, for example, according to DE-OS-2 353 737.
  • the pressure valve 1 has a connecting piece 4, which has an external thread 5 at one end and is screwed with this into a threaded bore 6 in the housing 2.
  • a delivery line 7 coaxially opens into the threaded bore from the pump work chamber of the fuel injection pump (not shown). This has a connection via the pressure valve 1 to a further delivery line 7 ', to the end of which an injection valve 8 is connected.
  • the connecting piece 4 is constructed essentially cylindrical and has an axial cylindrical recess 9 which is open towards the screw-in side. Coaxial to the cylindrical recess 9 there is a connection bore 11 which opens into a connection nipple 12 of the connection piece and connects the recess 9 to the delivery line 7 'or the injection valve 8.
  • a tubular valve seat body 14 is inserted into the axial recess 9, which has a collar 15 at its end, at the end of the pump work space, by means of which it is held by the end 16 of the connecting piece from the shoulder 17 on the bottom of the threaded bore 6.
  • the tubular valve seat body 14 has a valve seat 19 on which a conical sealing surface 20 of a valve closing member 21 of the pressure valve comes to rest.
  • the valve closing member has, in a known manner, wing-shaped guide surfaces 23 which are guided in the axial bore 24 of the valve seat body 14 and between which fuel can pass to the valve seat.
  • the valve closing member is designed as a cylinder 25, which is significantly reduced in diameter compared to the diameter of the bore 24.
  • the valve closing member has a collar 26 which is fitted into the bore 24 of the valve seat body.
  • the collar 26 On its outer circumference, the collar 26 has a bevel 27 which produces a throttle connection between the part of the cylinder 25 on the guide surface side and the part on the sealing surface side.
  • the valve closing member 21 also has coaxially a relief channel 28 which on the one hand has an outlet 30 on the part of the cylinder 25 on the guide surface side and on the other hand opens centrally on the end face of a pin 31. This sits on an end face 32 of the valve closing member, which adjoins the sealing surface 20 and that Valve closing member limited to the interior of the recess 9.
  • the pin 31 serves to center a cup-shaped part 34, the cylindrical wall of which merges into an outer collar 35 which is placed flush on the end face 32.
  • the pin 31 protrudes into the cylindrical interior 36 of the cup-shaped part 34.
  • On the outer collar 35 is a closing spring 37, which on the other hand is supported on the end face 38 of the recess 9 and holds the cup-shaped part 34 in a positive connection with the valve closing member 21 and endeavors to keep this with its sealing surface 20 on the valve seat 19.
  • the cup-shaped part 34 can also be connected to the valve closing member in some other way. B. also serve a weld.
  • a check valve 46 is provided with a closing spring 40, which is supported on the one hand on the end face of the pin 31 and on the other hand acts on a valve plate 41 which serves to guide a spherical valve closing member 42.
  • This has a seat in a conical recess 43 at the bottom of the pot-shaped part, this recess merging into a throttle 44 which opens into the spring chamber 45 of the recess 9 receiving the pressure valve closing spring 37.
  • valve closing member 21 is raised under the influence of the pressure of the fuel supplied via the delivery line 7, as shown in the figure. If only a small amount of fuel is pumped per unit of time, this can flow past the bevel 27 through the throttle connection without the collar 26 having to be completely removed from the bore 24.
  • the valve is only raised slightly, as shown in the drawing, and yet a pressure builds up in the delivery line 7 ′, which is above the opening pressure of the injection valve 8 and causes an injection. At the end of the delivery stroke, the pressure collapses on the pump side, so that the valve closing member 21 is brought into the closed position under the action of the valve closing spring 37.
  • the collar 26, which is also referred to as a suck-back collar, draws fuel back from the area upstream of the valve seat 19 in accordance with its previous stroke until the valve closing member comes into the closed position.
  • the amount of suckback is reduced by the amount of fuel that flows as a compensating flow through the throttle connection 27 during this movement. In this way, the fuel is relieved in the delivery line between the valve closing member and the injection valve 8 in a known manner.
  • pressure waves run in a known manner through the delivery line 7 due to the dynamic conditions, which are reflected on the valve closing member 21 and run back and forth between the injection valve and valve closing member.
  • These pressure waves can reach pressure values that are higher than the opening pressure of the injection valve, so that fuel can be re-injected without additional measures, as already described at the beginning.
  • the average pressure in the delivery line is then still greater than the closing pressure of the injection valve due to the dynamic pressure conditions.
  • the peak pressures of the pressure waves are higher, the higher the total residual pressure in the delivery line 7 'after the Ventitschtiessgtieds 21 has been shot.
  • a check valve 46 creates a connection from the spring chamber 45 or the delivery line 7 ′ to the delivery line 7 on the pump work chamber side beyond the valve closing member 21 when the opening pressure of this check valve is exceeded.
  • a certain amount of fuel can flow away via the throttle 44, which causes a reduction of the pressure wave that has arrived.
  • the wave then reflected towards the injection valve has pressure values that are not above the opening pressure of the injection valve.
  • the throttle influence of the throttle connection 27 increases in such a way that the suckback collar 26 emerges from the bore 24 and the delivered fuel can flow unthrottled past the suckback collar into the spring chamber 45.
  • the full valve closing member stroke is effective for sucking back fuel quantities.
  • the relief association essentially takes over the relief of the injection line to prevent post-injection alone.
  • the amount of relief is then essentially a relief volume of the valve stroke x free ring area of the end face of the relief collar 26. Furthermore, during the rapid stroke movement of the valve closing member, no substantial compensation amounts flow past the throttle connection 27, so that the delivery line is maximally relieved.
  • the throttle connection 27 on the return suction collar can also be produced with the aid of an increased play between collar 26 and bore 24 or through bores in the collar itself.
  • the closing member 21 would first have to carry out the full stroke, which corresponds to the relief stroke; until the connection from the conveyor line 7 to the conveyor line 7 'is established.
  • the low delivery rate would result in a delayed injection point.
  • the delivery line 7 ' would be relieved in particular in the same way as the closing member, as is the case with partial load or full load or with high delivery rates. This relief corresponds to a swallowing volume which is high for a low delivery rate during idling operation and which has to be filled up until a pressure is reached in the delivery line 7 'which corresponds to the opening pressure of the injection valve.
  • a spray delay would also occur here and a correspondingly long pre-delivery stroke would be required for the pump piston.
  • This long pre-delivery stroke which due to the low delivery rate achieved by the silent running device is even greater than in normal operation without a silent running device, makes it necessary for the injection pump to provide a relatively large useful stroke, the stroke which is effective for fuel delivery to the fuel injection nozzle got to.
  • this useful stroke for idling is lost to the useful stroke in the rest of the load range. This complicates the use of a silent running device to a considerable extent or requires a complex pump design with a high useful stroke.
  • the delivery line 7 ' is relieved only slightly at low delivery rates, particularly in the area of quiet operation.
  • the check valve 46 is provided, via which the pressure peaks are reduced in this operating range by fuel being throttled by the throttle 44 when the check valve is open, the interior 36 and the relief channel 35 can flow back to the pump work space via the outlet 30.
  • a desired residual pressure can be maintained in the various operating areas of the internal combustion engine in the delivery line 7 'without the opening pressure of the injection nozzles being exceeded after they are closed .
  • the opening pressure of the check valve is advantageously chosen so that it is approximately as large as the injection valve closing pressure. This means that a very high stand pressure or residual pressure in the delivery line can be maintained with the lowest absorption volume.
  • long spray times are obtained in idle-quiet operation, without these being as large as with a pressure valve which has no check valve. In this case, very high residual pressures would remain in the delivery lines 7 'because of the throttle connection 27 and thus very long spraying times would occur, some of which would be extended by post-spraying.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fuel-Injection Apparatus (AREA)
  • Check Valves (AREA)

Description

Die Erfindung geht von einem Druckventil nach der Gattung des Hauptanspruchs aus. Bei einem solchen durch die CH-PS-394 710 bekannten Druckventil soll das sogenannte Nachtropfen oder Nachspritzen von Kraftstoff nach Beendigung des wirksamen Förderhubs des Einspritzpumpenkolbens dadurch verhindert werden, daß an dem Druckventil ein Rücksaugbund in Kombination mit einer gegebenenfalls durch ein Druckhalteventil gesteuerten Entlastungsdrossel vorgesehen ist. Ohne diese Maßnahme würden nach Beendigung des wirksamen Förderhubs des Pumpenkolbens dem ein Schließen des Druckventils und des Hochdruckeinspritzventils folgt, Druckwellen in der Kraftstofforderleitung zwischen Druckventil und Einspritzventil entstehen, die zwischen Einspritzventil und Druckventil hin- und herlaufen. Die vom Druckventil zum Einspritzventil hin reflektierten, zurücklaufenden Wellen können dieses nachträglich öffnen, so daß es dabei zu Kraftstoffaustritten mit den bekannten Nachteilen kommt.The invention is based on a pressure valve according to the preamble of the main claim. In such a pressure valve known from CH-PS-394 710, the so-called dripping or re-injection of fuel after the effective delivery stroke of the injection pump piston is to be prevented by providing a return suction collar on the pressure valve in combination with a relief throttle, optionally controlled by a pressure-maintaining valve . Without this measure, after the effective delivery stroke of the pump piston has ended, which is followed by a closing of the pressure valve and the high-pressure injection valve, pressure waves would occur in the fuel supply line between the pressure valve and the injection valve, which would reciprocate between the injection valve and the pressure valve. The returning waves reflected from the pressure valve to the injection valve can subsequently open it, so that fuel leaks occur with the known disadvantages.

Die Verwendung eines Rücksaugbundes allein ist dort als Maßnahme gegen diese nachteilige Wirkung nur bei kleinen Einspritzmengen pro Einspritzhub des Pumpenkolbens wirksam.The use of a return suction collar alone is effective there as a measure against this disadvantageous effect only with small injection quantities per injection stroke of the pump piston.

Die bekannte Ausgestaltung hat nur den Zweck, das Nachspritzen oder Nachtropfen zu verhindern, und zwar in einem weiten Bereich der Einspritzmengensteuerung pro Einspritzhub. Dabei hat bei der Ausgestaltung die nicht durch ein Druckhalteventil gesteuerte Entlastungsdrossel die Auswirkung, daß der Restdruck in der Kraftstofförderleitung sich mit der Drehzahl stark ändert. Bei kleinen Einspritzmengen wird weiterhin die Förderleitung zwischen Druckventil und Einspritzventil in gleichem Weise entlastet wie bei großen Einspritzmengen. Beim anschließenden Förderhub ist dann ein mehr oder weniger großes Schluckvolumen wirksam, das durch die Pumpenkolbenförderung aufgefüllt werden muß, bis der Einspritzdruck am Einspritzventil erreicht ist. Dies führt insbesondere bei kleinen Einspritzmengen in nachteiliger Weise einmal wegen der unterschiedlichen Restdrücke zu merklichen Mengenstreuungen, die sich nachteilig auf das Laufverhalten der Brennkraftmaschine auswirken. Zum anderen geht ein Teil des Nutzhubes des Pumpenkolbens verloren.The known configuration has only the purpose of preventing the injection or dripping, namely in a wide range of the injection quantity control per injection stroke. In the embodiment, the relief throttle, which is not controlled by a pressure control valve, has the effect that the residual pressure in the fuel delivery line changes greatly with the speed. With small injection quantities, the delivery line between the pressure valve and the injection valve is relieved in the same way as with large injection quantities. During the subsequent delivery stroke, a more or less large swallowing volume is effective, which has to be filled up by the pump piston delivery until the injection pressure at the injection valve is reached. In the case of small injection quantities in particular, this disadvantageously leads to noticeable quantity spreads due to the different residual pressures, which have a disadvantageous effect on the running behavior of the internal combustion engine. On the other hand, part of the useful stroke of the pump piston is lost.

Dies wirkt sich insbesondere dann nachteilig aus, wenn an der Kraftstoffeinspritzpumpe eine sogenannte Leiselaufeinrichtung verwirklicht ist, mit der die Förderrate des Pumpenkolbens reduziert werden soll. Dazu wird in bekannter Weise ein Teil des vom Pumpenkolben geförderten Kraftstoffs entnommen und dabei zur Erzielung der gewünschten Einspritzmenge die Förderdauer verlängert. Dies führt zu einem weichen Brennverhalten. Für eine lange Förderdauer ist anderer seits jedoch ein großer Pumpenkolbenförderhub für diesen Leiselaufbetriebsbereich notwendig, der in der Regel dem Leerlaufbetriebsbereich entspricht. Wenn nun ein Teil des wirksamen Förderhubs des Pumpenkolbens für das Auffüllen der Schluckvolumina benötigt wird, ist der erforderliche Gesamthub des Pumpenkolbens zur Einhaltung auch großer Vollasteinspritzmengen sehr groß auszulegen, was sich nachteilig auf die Bauweise der Kraftstoffeinspritzpumpe auswirkt.This is particularly disadvantageous when a so-called quiet running device is implemented on the fuel injection pump, with which the delivery rate of the pump piston is to be reduced. For this purpose, part of the fuel delivered by the pump piston is removed in a known manner and the delivery period is extended in order to achieve the desired injection quantity. This leads to a soft burning behavior. For a long delivery period, on the other hand, however, a large pump piston delivery stroke is necessary for this silent operating range, which generally corresponds to the idling operating range. If a part of the effective delivery stroke of the pump piston is now required to fill up the swallowing volume, the required total stroke of the pump piston must be designed to be large in order to maintain even large full-load injection quantities, which has a disadvantageous effect on the design of the fuel injection pump.

Bei dem eingangs genannten bekannten Druckventil ist im übrigen als Führungsteil des Druckventilschließglieds ein in den Durchgangskanal des Ventilkörpers eingepaßter Zylinder vorgesehen. Die Kraftstofförderung bei geöffnetem Druckventil erfolgt dann über den axialen Entlastungskanal stromaufwärts der Drossel und einem Querkanal, der den Entlastungskanal mit einer den Rücksaugbund vom Führungsteil trennenden Ringnut verbindet. Auf diese Weise ist eine Entlastung des Federraums nur über den koaxial durch das ganze Ventilschließglied gehenden Entlastungskanal möglich.In the known pressure valve mentioned at the outset, a cylinder fitted into the passage channel of the valve body is provided as the guide part of the pressure valve closing element. The fuel delivery with the pressure valve open then takes place via the axial relief channel upstream of the throttle and a transverse channel which connects the relief channel to an annular groove separating the suction collar from the guide part. In this way, relief of the spring chamber is only possible via the relief channel which extends coaxially through the entire valve closing member.

Es ist weiterhin durch die US-PS-2 706 490 bekannt, bei einem Druckventil, das mit einem Rücksaugbund versehen ist, durch den die Kraftstofförderleitung nach Spritzende entlastet werden kann, am Rücksaugbund eine Drosselverbindung vorzusehen. Ein solchermaßen aus gebildetes Ventilschließglied des Druckventils ist für Brennkraftmaschinen vorgesehen, die mit Flüssigkraftstoff und gasförmigem Kraftstoff zugleich betrieben werden sollen. Der Flüssigkraftstoff wird dabei als Zündkraftstoff in sehr geringer Menge in die Brennräume der Brennkraftmaschine eingespritzt und zur Zündung gebracht. In der Folge wird dann die Gasfüllung entflammt. Zugleich soll aber eine solche Brennkraftmaschine auch im gesamten Betriebsbereich mit Flüssigkraftstoff betrieben werden können. Die Drosselverbindung am Ventilschließglied des Druckventils soll dann verhindern, daß bei der Zündkraftstoffeinspritzung sich das Ventilschließglied um den Betrag hebt, der dem Entlastungsvolumen ohne Drossel entspreche. Es soll somit verhindert werden, daß bei Spritzende die Kraftstoffförderleitung um den vollen Betrag des durch den Entlastungsbund zur Verfügung gestellten Entlastungsvolumens entlastet wird. Diese Entlastung würde zu einem unbefriedigenden Betriebsergebnis führen. Durch die Drosselverbindung soll in dem Betriebsbereich, bei dem Zündkraftstoff eingespritzt werden soll, die Entlastung voll ausgeschaltet werden, indem ohne merkliches Druckgefelle die Zündkraftstoffmenge über die Drosselverbindung am Entlastungsbund vorbeifließt. Bei reinem Flüssigkraftbetrieb soll hingegen die Entlastung durch den Rücksaugbund voll zur Wirkung kommen.It is also known from US Pat. No. 2,706,490 to provide a throttle connection on a pressure valve which is provided with a return suction collar, through which the fuel delivery line can be relieved after the end of the spray, on the return suction collar. A valve closing member of the pressure valve formed in this way is provided for internal combustion engines which are to be operated with liquid fuel and gaseous fuel at the same time. The liquid fuel is injected as ignition fuel in a very small amount into the combustion chambers of the internal combustion engine and brought to ignition. As a result, the gas filling is ignited. At the same time, however, such an internal combustion engine should also be able to be operated with liquid fuel in the entire operating range. The throttle connection on the valve closing member of the pressure valve is then intended to prevent the valve closing member from lifting during ignition fuel injection by the amount which corresponds to the relief volume without the throttle. This is to prevent the fuel delivery line from being relieved by the full amount of the relief volume made available by the relief association at the end of the spray. This relief would lead to an unsatisfactory operating result. The throttle connection is intended to switch off the discharge completely in the operating range in which ignition fuel is to be injected, in that the amount of ignition fuel flows past the relief collar via the throttle connection without any noticeable pressure drops. In the case of pure liquid power operation, on the other hand, the relief provided by the return suction collar should take full effect.

Diese Ausgestaltung hat jedoch den Nachteil, daß sie keinen allzu großen Änderungsbereich der Einspritzmenge zuläßt. Bei großen Einspritzmengen und bei vollem Flüssigkraftstoffbetrieb ist die Wirkung des Rücksaugbundes durch die Drosselverbindung merklich reduziert. Bei großen Einspritzmengen pro Hub und bei kleinen Drehzahlen kann es dabei doch zu hohen Restdrücken in der Kraftstofförderleitung und zu Druckwellen kommen, die vom Druckventil reflektiert werden und zu einem unkontrollierten Öffnen der Einspritzdüsen führen. Der dabei nachträglich austretende Kraftstoff wird schlecht aufbereitet, tritt zu spät in den Brennraum ein und nimmt nicht mehr vollständig an der Verbrennung teil. Dies führt zu rauchender Verbrennung und zu Düsenverkokung, wobei letzteres wiederum eine weitere Verlängerung der Einspritzzeiten nach sich zieht. Das Betriebsverhalten und der Wirkungsgrad der Verbrennung werden somit Verschlechtert.However, this configuration has the disadvantage that it does not allow an excessively large range of changes in the injection quantity. For large ones Injection quantities and at full fuel operation Flüssigkraf t the effect of Rücksaugbundes is markedly reduced by the throttle connection. With large injection quantities per stroke and at low speeds, high residual pressures in the fuel delivery line and pressure waves can occur, which are reflected by the pressure valve and lead to an uncontrolled opening of the injection nozzles. The subsequently exiting fuel is poorly prepared, enters the combustion chamber too late and no longer fully participates in the combustion. This leads to smoking combustion and nozzle coking, which in turn leads to a further increase in injection times. The operating behavior and the efficiency of the combustion are thus deteriorated.

Auch durch die FR-A-1 050 441 ist ein Druckventil bekannt, in dem ein Rückschlagventil integriert ist. Abweichend jedoch vom durch die CH-A-394 710 bekannten Druckventil weist dieses Druckventil kein Schließglied auf, das einen durchgehenden Entlastungskanal hat. Das Rückschlagventil dieses bekannten Druckventil schließt einen zur Einspritzseite führenden Kanal ab und ist ventilfederseitig mit einer Druckkammer verbunden, die zwischen einem Kopf und einem Rücksaugbund des Druckventil schließgliedes im Durchgangskanal des Druckventils eingeschlossen ist. Der Kopf bei diesem bekannten Druckventilschließglied weist einen zylindrischen Teil auf, der im Schließzustand innerhalb einer gegenüber dem Durchmesser des Ventilsitzes erweiterten zylindrischen Bohrung liegt. Je nach dem, ob mit so einem Ventil eine Voreinspritzung oder nur ein Druckabbau zur Vermeidung von Nachspritzen bezweckt werden soll, weist der zylindrische Teil zur zylindrischen Bohrung einen Ringspalt auf oder er ist dicht eingepaßt. Im letztgenannten Fall wird kurzzeitig mit Förderbeginn die Förderrate derart erhöht, daß es zu einer Voreinspritzung kommt, die dann abgebrochen wird, wenn der zylindrische Teil des Druckventilschließgliedes aus der zylindrischen Bohrung austaucht und der verbleibende Teil auf das herrschende Druckniveau aufgefüllt werden muß. Das Rückschlagventil hat die Aufgabe, daß die Öffnungsbewegung auch dann, wenn genügend Spiel zwischen zylindrischem Teil und zylindrischer Bohrung vorhanden ist, nicht behindert wird. Beim Öffnen des Ventils kann mit Hilfe des Rückschlagventils ein Druckausgleich zum eingeschlossenen Raum erfolgen. Beim Schließvorgang bleibt dieses Ventil geschlossen und es erfolgt dann beim Eintauchen des zylindrischen Teils in die zylindrische Bohrung eine Dämpfungsaktion des Druckventilschließgliedes, indem aus dem dann eingeschlossenen Raum Kraftstoff über den Ringspalt zwischen zylindrischem Teil und zylindrischer Bohrung zur Einspritzseite hin entweichen muß. In dem Falle allerdings, in dem eine Voreinspritzung erwünscht ist, ist der zylindrische Teil des Kopfes des Druckventilschließgliedes im wesentlichen dicht in der zylindrischen Bohrung geführt. Um auch hier eine Dämpfung beim Schließvorgang des Druckventils und damit einen Abbau von Druckwellen in der Einspritzleitung zu bekommen, wurde vorgeschlagen, ein Teil des zylindrischen Teils mit einem vergrößerten Spiel zu versehen. Dieses Druckventil und auch die übrigen Lösungsvorschläge gemäß der FR-A-1 050 441 dienen insgesamt dem Zweck, eine gedämpfte Schließbewegung des Ventilschließgliedes zu erzielen, um somit Druckwellen in der Einspritzleitung nach Förderende abzubauen in Ergänzung zur Volumenentlastung durch einen Rücksaugbund, statt wie bei dem Druckventil gemäß der CH-A-394 710 ein Rückschlagventil, als Gleichdruckventil dienend, zu verwenden. Mit diesem Ventil kann der Druck in der Förderleitung nicht generell auf einen Höchstwert begrenzt werden. Der tatsächliche Hub des Ventils entspricht in all den Fällen, in denen die Dämpfungseinrichtung durch Entlastung zum Einspritzventil hin erfolgt, der geförderten Kraftstoffeinspritzmenge. Somit wird die Förderleitung bei kleinen Einspritzmengen relativ hoch entlastet analog zur Entlastung bei höheren Einspritzmengen. Wie bereits eingangs beschrieben, ergeben sich aus diesem Grunde wegen unterschiedlich aufzufüllender Restdrücke merkliche Mengenstreuungen, die ein Anpassen der Kraftstoffeinspritzmenge an den jeweiligen Bedarf in verschiedenen Betriebspunkten erschweren. Erfolgt die Entlastung des eingeschlossenen Raumes bei dem bekannten Ventil zur Pumpenarbeitsraumseite, so macht sich hier vor allem auch der Drehzahleinfluß auf die Drosselwirkung dieser Entlastung bemerkbar.A pressure valve is also known from FR-A-1 050 441, in which a check valve is integrated. However, in deviation from the pressure valve known from CH-A-394 710, this pressure valve has no closing element which has a continuous relief channel. The check valve of this known pressure valve closes a channel leading to the injection side and is connected on the valve spring side to a pressure chamber which is enclosed between a head and a suction collar of the pressure valve closing member in the through channel of the pressure valve. The head in this known pressure valve closing member has a cylindrical part which, in the closed state, lies within a cylindrical bore which is enlarged compared to the diameter of the valve seat. Depending on whether the purpose of such a valve is to pre-injection or only to reduce pressure to avoid post-injection, the cylindrical part has an annular gap with the cylindrical bore or it is tightly fitted. In the latter case, the delivery rate is increased briefly at the start of delivery in such a way that a pre-injection occurs, which is terminated when the cylindrical part of the pressure valve closing member emerges from the cylindrical bore and the remaining part has to be filled up to the prevailing pressure level. The check valve has the task that the opening movement is not impeded even when there is sufficient play between the cylindrical part and the cylindrical bore. When the valve is opened, the check valve can be used to equalize the pressure in the enclosed space. During the closing process, this valve remains closed and then when the cylindrical part is immersed in the cylindrical bore, a damping action of the pressure valve closing member takes place, in that fuel must escape from the then enclosed space through the annular gap between the cylindrical part and the cylindrical bore to the injection side. However, in the case where a pre-injection is desired, the cylindrical part of the head of the pressure valve closing member is guided essentially tightly in the cylindrical bore. In order to get a damping during the closing of the pressure valve and thus a reduction of pressure waves in the injection line, it was proposed to provide a part of the cylindrical part with increased play. Overall, this pressure valve and the other proposed solutions according to FR-A-1 050 441 serve the purpose of achieving a damped closing movement of the valve closing element, in order to reduce pressure waves in the injection line after the end of delivery, in addition to the volume relief by means of a suction collar, instead of as in the case of the Pressure valve according to CH-A-394 710 to use a check valve, serving as a constant pressure valve. With this valve, the pressure in the delivery line cannot generally be limited to a maximum value. The actual stroke of the valve corresponds in all cases in which the damping device is relieved to the injection valve to the delivered fuel injection quantity. Thus, the delivery line is relieved of relatively high loads with small injection quantities analogous to the relief for larger injection quantities. As already described at the outset, this results in noticeable quantity spreads due to different residual pressures to be filled, which make it difficult to adapt the fuel injection quantity to the respective requirement at different operating points. If the enclosed space is relieved in the known valve on the pump workspace side, the speed influence on the throttling effect of this relief is particularly noticeable here.

Vorteile der ErfindungAdvantages of the invention

Das erfindungsgemäße Druckventil mit den kennzeichnenden Merkmalen des Hauptanspruchs hat demgegenüber den Vorteil, daß durch das Rückschlagventil der Druck in der Förderleitung generell auf einen Höchstwert begrenzt wird, der kleiner ist als der Öffnungsdruck des Kraftstoffeinspritzventils, so daß kein Nachspritzen auftreten kann. Durch die Ausgestaltung des Rücksaugbundes wird erreicht, daß bei kleinen Einspritzmengen bzw. bei geringer Förderrate des vom Pumpenarbeitsraum zu dem Einspritzventil geförderten Kraftstoffs der Kraftstoff über die Drosselverbindung überströmen kann, ohne daß dabei das Ventilschließglied des Druckventils wesentlich von seinem Sitz abgehoben wird. Dementsprechend klein ist dann auch der Entlastungshub bzw. die Wirkung des Entlastungsbundes beim Schließen des Druckventils, so daß ein relativ hoher Restdruck in der Förderleitung erhalten bleibt. Damit dieser Restdruck jedoch den Öffnungsdruck der Einspritzventile nicht überschreitet, ist hier wesentlich die Wirkung des Rückschlagventils. Bei größerem Einspritzmengen bzw. größeren Förderraten oder bei höheren Drehzahlen erhöht sich die Drosselwirkung der Drosselverbindung derart, daß hier kaum mehr die Bewegung des Schließgliedes des Druckventils beeinflussende Kraftstoffmengen überströmen. Im Teillastbereich bzw. Vollastbereich kommt somit der Rücksaugbund voll zur Wirkung, derart, daß auch die Wirkung des Rückschlagventils nicht mehr zur Einhaltung eines Restdrucks unterhalb des Düsenöffnungsdruckes von tragender Bedeutung ist.The pressure valve according to the invention with the characterizing features of the main claim has the advantage that the pressure in the delivery line is generally limited to a maximum value by the check valve, which is less than the opening pressure of the fuel injector, so that no post-injection can occur. The configuration of the return suction collar ensures that, with small injection quantities or with a low delivery rate of the fuel delivered from the pump work chamber to the injection valve, the fuel can flow over the throttle connection without the valve closing member of the pressure valve being lifted substantially from its seat. The relief stroke or the effect of the relief collar when the pressure valve is closed is then correspondingly small, so that a relatively high residual pressure remains in the delivery line. So that this residual pressure does not exceed the opening pressure of the injection valves, the effect of the check valve is essential here. With larger injection quantities or larger delivery rates or at higher speeds, the throttling effect of the throttle connection increases in such a way that fuel quantities influencing the movement of the closing element of the pressure valve hardly overflow here. In the partial-load range or full-load range, the return suction collar thus comes into full effect in such a way that the effect of the check valve is no longer of fundamental importance for maintaining a residual pressure below the nozzle opening pressure.

Dadurch, daß bei kleiner Förderrate ein relativ hoher Restdruck in der Förderleitung eingehalten werden kann, wird dementsprechend auch das schädliche Schluckvolumen reduziert. Man erhält somit bei gleichbleibender Einspritzmenge eine gleichmäßig lange Förderphase des Pumpenkolbens. Dies ist insbesondere dann von Bedeutung, wenn die Brennkraftmaschine mit einer sogenannten, schon eingangs erwähnten Leiselaufeinrichtung betrieben wird. Bei solchen Einspritzpumpen soll zwecks Einhalten eines sich ebenfalls auf das Geräusch auswirkenden exakten Spritzbeginns die Kraftstofförderung auch mit dem wirksamen Förderhub des Pumpenkolbens einsetzen. Dies gilt insbesondere ebenfalls für den kritischen Bereich des Leerlaufes und der geringen Last und wird durch den mit der erfindungsgemäßen Einrichtung erzielbaren hohen Restdruck erreicht. Auch wird dabei ein Nutzhubverlust, der insbesondere nachteilig für den Leerlaufbetrieb ist, vermieden. Mit der erfindungsgemäßen Ausgestaltung können die Anforderungen in allen Betriebsbereichen einer Brennkraftmaschine, die insbesondere mit einer Leiselaufeinrichtung betrieben wird, erfüllt werden und es kann das Arbeitsvermögen in bezug auf den Nutzhub der Kraftstoffversorgungseinrichtung optimal ausgenutzt werden. Durch den mit dem erfindungsgemäßen Druckventil steuerbaren Restdruck in der Förderleitung kann beliebig auf die Spritzdauer bei gegebenem Einspritzdüsen-Austrittsquerschnitt Einfluß genommen werden.Because a relatively high residual pressure can be maintained in the delivery line at a low delivery rate, the harmful swallowing volume is accordingly reduced. Thus, with a constant injection quantity, the pump piston delivers a uniformly long delivery phase. This is particularly important when the internal combustion engine is operated with a so-called quiet running device, as already mentioned. In the case of such injection pumps, in order to maintain an exact start of injection, which also affects the noise, the fuel delivery should also be used with the effective delivery stroke of the pump piston. This also applies in particular to the critical range of idling and the low load and is achieved by the high residual pressure that can be achieved with the device according to the invention. A useful stroke loss, which is particularly disadvantageous for idle operation, is also avoided. With the configuration according to the invention, the requirements can be met in all operating areas of an internal combustion engine, which is operated in particular with a silent running device, and the working capacity in relation to the useful stroke of the fuel supply device can be optimally utilized. The residual pressure in the delivery line, which can be controlled with the pressure valve according to the invention, can be used to influence the duration of the spray at a given cross section of the injection nozzle.

Durch die in den Unteransprüchen aufgeführten Maßnahmen sind vorteilhafte Ausgestaltungen der Erfindung und Weiterbildung der im Hauptanspruch angegebenen Lösung gekennzeichnet.Advantageous refinements of the invention and further development of the solution specified in the main claim are characterized by the measures listed in the subclaims.

Zeichnungdrawing

Ein Ausführungsbeispiel der Erfindung ist in der Zeichnung dargestellt und wird in der nachfolgenden Beschreibung naher erläutert.An embodiment of the invention is shown in the drawing and is explained in more detail in the following description.

Beschreibungdescription

Die Figur zeigt einen Längsschnitt durch ein Druckventil 1, das in das Gehäuse 2 einer nicht weiter dargestellten Kraftstoffeinspritzpumpe eingeschraubt ist, die beispielsweise gemäß DE-OS-2 353 737 aufgebaut ist. Das Druckventil 1 weist einen Anschlußstutzen 4 auf, der an seinem einen Ende ein Außengewinde 5 hat und mit diesem in eine Gewindebohrung 6 im Gehäuse 2 eingeschraubt ist. Koaxial mündet in die Gewindebohrung vom nicht weiter dargestellten Pumpenarbeitsraum der Kraftstoffeinspritzpumpe her eine Förderleitung 7. Diese hat über das Druckventil 1 eine Verbindung zu einer weiterführenden Förderleitung 7', an deren Ende ein Einspritzventil 8 angeschlossen ist.The figure shows a longitudinal section through a pressure valve 1, which is screwed into the housing 2 of a fuel injection pump, not shown, which is constructed, for example, according to DE-OS-2 353 737. The pressure valve 1 has a connecting piece 4, which has an external thread 5 at one end and is screwed with this into a threaded bore 6 in the housing 2. A delivery line 7 coaxially opens into the threaded bore from the pump work chamber of the fuel injection pump (not shown). This has a connection via the pressure valve 1 to a further delivery line 7 ', to the end of which an injection valve 8 is connected.

Der Anschlußstutzen 4 ist im wesentlichen zylindrisch aufgebaut und hat eine axiale zylindrische Ausnehmung 9, die zur Einschraubseite hin offen ist. Koaxial zur zylindrischen Ausnehmung 9 geht von dieser eine Anschlußbohrung 11 ab, die in einem Anschlußnippel 12 des Anschlußstutzens mündet und die Ausnehmung 9 mit der Förderleitung 7' bzw. dem Einspritzventil 8 verbindet.The connecting piece 4 is constructed essentially cylindrical and has an axial cylindrical recess 9 which is open towards the screw-in side. Coaxial to the cylindrical recess 9 there is a connection bore 11 which opens into a connection nipple 12 of the connection piece and connects the recess 9 to the delivery line 7 'or the injection valve 8.

Vom pumpenarbeitsraumseitigen Ende her ist in die axiale Ausnehmung 9 ein rohrförmiger Ventilsitzkörper 14 eingesetzt, der an seinem pumpenarbeitsraumseitigen Ende einen Bund 15 aufweist, über den er durch die pumpenarbeitsraumseitige Stirnseite 16 des Anschlußstutzens ab einer Schulter 17 am Grund der Gewindebohrung 6 gehalten wird. Am in die axiale Ausnehmung 9 ragenden stirnseitigen Ende weist der rohrförmige Ventilsitzkörper 14 einen Ventilsitz 19 auf, auf dem eine kegelförmige Dichtfläche 20 eines Ventilschließgliedes 21 des Druckventils zur Anlage kommt. Das Ventilschließglied weist in bekannter Weise flügelförmige Führungsflächen 23 auf, die in der axialen Bohrung 24 des Ventilsitzkörpers 14 geführt werden und zwischen denen Kraftstoff zum Ventilsitz hin durchtreten kann. Zwischen der kegelförmigen Dichtfläche 20 und den Führungsflächen 23 ist das Ventilschließglied als Zylinder 25 ausgeführt, der im Durchmesser gegenüber dem Durchmesser der Bohrung 24 wesentlich reduziert ist. Im Bereich des Zylinders 25 weist das Ventilschließglied einen Bund 26 auf, der in die Bohrung 24 des Ventilsitzkörpers eingepaßt ist. An seinem Außenumfang weist der Bund 26 einen Anschliff 27 auf, der eine Drosselverbindung zwischen dem führungsflächenseitigen Teil des Zylinders 25 und dem dichtflächenseitigen Teil herstellt.From the end of the pump work space, a tubular valve seat body 14 is inserted into the axial recess 9, which has a collar 15 at its end, at the end of the pump work space, by means of which it is held by the end 16 of the connecting piece from the shoulder 17 on the bottom of the threaded bore 6. At the front end projecting into the axial recess 9, the tubular valve seat body 14 has a valve seat 19 on which a conical sealing surface 20 of a valve closing member 21 of the pressure valve comes to rest. The valve closing member has, in a known manner, wing-shaped guide surfaces 23 which are guided in the axial bore 24 of the valve seat body 14 and between which fuel can pass to the valve seat. Between the conical sealing surface 20 and the guide surfaces 23, the valve closing member is designed as a cylinder 25, which is significantly reduced in diameter compared to the diameter of the bore 24. In the area of the cylinder 25, the valve closing member has a collar 26 which is fitted into the bore 24 of the valve seat body. On its outer circumference, the collar 26 has a bevel 27 which produces a throttle connection between the part of the cylinder 25 on the guide surface side and the part on the sealing surface side.

Das Ventilschließglied 21 weist weiterhin koaxial einen Entlastungskanal 28 auf, der einerseits einen Austritt 30 am führungsflächenseitigen Teil des Zylinders 25 hat und andererseits zentrisch auf der Stirnseite eines Zapfens 31 mündet. Dieser sitzt auf einer Stirnseite 32 des Ventilschließgliedes, die sich an die Dichtfläche 20 anschließt und das Ventilschließglied zum Innern der Ausnehmung 9 begrenzt.The valve closing member 21 also has coaxially a relief channel 28 which on the one hand has an outlet 30 on the part of the cylinder 25 on the guide surface side and on the other hand opens centrally on the end face of a pin 31. This sits on an end face 32 of the valve closing member, which adjoins the sealing surface 20 and that Valve closing member limited to the interior of the recess 9.

Der Zapfen 31 dient zur Zentrierung eines topfförmigen Teils 34, dessen zylindrische Wand in einen Außenbund 35 übergeht, der bündig auf die Stirnseite 32 aufgesetzt ist. Der Zapfen 31 ragt dabei in den zylindrischen Innenraum 36 des topfförmigen Teils 34. Auf den Außenbund 35 setzt eine Schließfeder 37 auf, die sich andererseits an der Stirnseite 38 der Ausnehmung 9 abstützt und den topfförmigen Teil 34 in schlüssiger Verbindung mit dem Ventilschließglied 21 halt und bestrebt ist, dieses mit seiner Dichtfläche 20 auf den Ventilsitz 19 zu halten. Der topfförmige Teil 34 kann aber auch mit dem Ventilschließglied anderweitig verbunden sein, Dazu kann z. B. auch eine Schweißnaht dienen.The pin 31 serves to center a cup-shaped part 34, the cylindrical wall of which merges into an outer collar 35 which is placed flush on the end face 32. The pin 31 protrudes into the cylindrical interior 36 of the cup-shaped part 34. On the outer collar 35 is a closing spring 37, which on the other hand is supported on the end face 38 of the recess 9 and holds the cup-shaped part 34 in a positive connection with the valve closing member 21 and endeavors to keep this with its sealing surface 20 on the valve seat 19. The cup-shaped part 34 can also be connected to the valve closing member in some other way. B. also serve a weld.

Im Innenraum 36 des topfförmigen Teils 34 ist ein Rückschlagventil 46 mit einer Schließfeder 40 vorgesehen, die sich einerseits auf der Stirnseite des Zapfens 31 abstützt und andererseits einen Ventilteller 41 beaufschlagt, der zur Führung eines kugelförmigen Ventilschließgliedes 42 dient. Dieses hat einen Sitz in einer kegelförmigen Ausnehmung 43 am Boden des topfförmigen Teils, wobei diese Ausnehmung in eine Drossel 44 übergeht, die in den die Druckventilschließfeder 37 aufnehmenden Federraum 45 der Ausnehmung 9 mündet.In the interior 36 of the pot-shaped part 34, a check valve 46 is provided with a closing spring 40, which is supported on the one hand on the end face of the pin 31 and on the other hand acts on a valve plate 41 which serves to guide a spherical valve closing member 42. This has a seat in a conical recess 43 at the bottom of the pot-shaped part, this recess merging into a throttle 44 which opens into the spring chamber 45 of the recess 9 receiving the pressure valve closing spring 37.

Wird beim Betrieb einer Kraftstoffeinspritzpumpe, Kraftstoff zum Einspritzventil 8 gefördert, so wird unter dem Einfluß des Druckes des über die Förderleitung 7 zugeführten Kraftstoffs das Ventilschließglied 21 angehoben, derart, wie es in der Figur gezeigt ist. Wird nun eine nur geringe Kraftstoffmenge pro Zeiteinheit gefördert, so kann diese durch die Drosselverbindung am Anschliff 27 vorbeiströmen, ohne daß der Bund 26 ganz aus der Bohrung 24 austauchen muß. Das Ventil wird nur leicht angehoben, wie in der Zeichnung dargestellt und dennoch in der Förderleitung 7' ein Druck aufgebaut, der über dem Öffnungsdruck des Einspritzventils 8 liegt und eine Einspritzung bewirkt. Am Ende des Förderhubs bricht der Druck pumpenseitig zusammen, so daß das Ventilschließglied 21 unter der Einwirkung der Ventilschließfeder 37 in Schließstellung gebracht wird. Dabei wird durch den Bund 26, der auch als Rücksaugbund bezeichnet wird, entsprechend seinem vorherigen Hub, Kraftstoff aus dem Bereich stromaufwärts des Ventilsitzes 19 zurückgesaugt, bis das Ventilschließglied in Schließstellung kommt. Die Rücksaugmenge reduziert sich dabei um den Kraftstoffteil, der bei dieser Bewegung als Ausgleichsströmung über die Drosselverbindung 27 fließt. Auf diese Weise erfolgt durch Kraftstoffentnahme eine Entlastung in der Förderleitung zwischen Ventilschließglied und Einspritzventil 8 in bekannter Weise.If fuel is fed to the injection valve 8 during operation of a fuel injection pump, the valve closing member 21 is raised under the influence of the pressure of the fuel supplied via the delivery line 7, as shown in the figure. If only a small amount of fuel is pumped per unit of time, this can flow past the bevel 27 through the throttle connection without the collar 26 having to be completely removed from the bore 24. The valve is only raised slightly, as shown in the drawing, and yet a pressure builds up in the delivery line 7 ′, which is above the opening pressure of the injection valve 8 and causes an injection. At the end of the delivery stroke, the pressure collapses on the pump side, so that the valve closing member 21 is brought into the closed position under the action of the valve closing spring 37. In this case, the collar 26, which is also referred to as a suck-back collar, draws fuel back from the area upstream of the valve seat 19 in accordance with its previous stroke until the valve closing member comes into the closed position. The amount of suckback is reduced by the amount of fuel that flows as a compensating flow through the throttle connection 27 during this movement. In this way, the fuel is relieved in the delivery line between the valve closing member and the injection valve 8 in a known manner.

Nach dem Schließen des Ventilschließglieds und des Einspritzventils aufgrund der unterbrochenen Kraftstoffförderung laufen aufgrund der dynamischen Verhältnisse in bekannter Weise Druckwellen durch die Förderleitung 7, die am Ventilschließglied 21 reflektiert werden und zwischen Einspritzventil und Ventilschließglied hin und her laufen. Diese Druckwellen können Druckwerte erreichen, die höher sind als der Öffnungsdruck des Einspritzventils, so daß es ohne zusätzliche Maßnahmen zu einem Nacheinspritzen von Kraftstoff kommen kann, wie bereits eingangs geschildert. Insbesondere ist auch, wenn es bereits zu einem Schließen des Einspritzventils gekommen ist, aufgrund der dynamischen Druckverhältnisse dann der mittlere Druck in der Förderleitung noch größer als der Schließdruck des Einspritzventils. Die Spitzendrücke der Druckwellen sind umso höher, je höher der gesamte Restdruck in der Förderleitung 7' nach Schtießen desVentitschtießgtieds21 bleibt.After the valve closing member and the injection valve have been closed due to the interrupted fuel delivery, pressure waves run in a known manner through the delivery line 7 due to the dynamic conditions, which are reflected on the valve closing member 21 and run back and forth between the injection valve and valve closing member. These pressure waves can reach pressure values that are higher than the opening pressure of the injection valve, so that fuel can be re-injected without additional measures, as already described at the beginning. In particular, if the injection valve has already been closed, the average pressure in the delivery line is then still greater than the closing pressure of the injection valve due to the dynamic pressure conditions. The peak pressures of the pressure waves are higher, the higher the total residual pressure in the delivery line 7 'after the Ventitschtiessgtieds 21 has been shot.

Durch das Vorsehen eines Rückschlagventils 46 wird bei Überschreiten des Öffnungsdrucks dieses Rückschlagventils eine Verbindung vom Federraum 45 bzw. der Förderleitung 7' zur pumpenarbeitsraumseiten Förderleitung 7 jenseits des Ventilschließglieds 21 hergestellt. Über die Drossel 44 kann dabei eine gewisse Kraftstoffmenge abfließen, die einen Abbau der angekommenen Druckwelle bewirkt. Die danach zum Einspritzventil hin reflektierte Welle weist Druckwerte auf, die nicht oberhalb des Öffnungsdrucks des Einspritzventils liegen.The provision of a check valve 46 creates a connection from the spring chamber 45 or the delivery line 7 ′ to the delivery line 7 on the pump work chamber side beyond the valve closing member 21 when the opening pressure of this check valve is exceeded. A certain amount of fuel can flow away via the throttle 44, which causes a reduction of the pressure wave that has arrived. The wave then reflected towards the injection valve has pressure values that are not above the opening pressure of the injection valve.

Bei größeren Kraftstoffeinspritzmengen und auch bei großen Förderraten entsprechend hoher Drehzahl verstärkt sich der Drosseleinfluß der Drosselverbindung 27 derart, daß der Rücksaugbund 26 aus der Bohrung 24 austaucht und der geförderter Kraftstoff ungedrosselt am Rücksaugbund vorbei in den Federraum 45 strömen kann. In diesem Fall ist bei Beendigung der Förderung der volle Ventilschließgliedhub für ein Rücksaugen von Kraftstoffmengen wirksam. Hier übernimmt der Entlastungsbund im wesentlichen die Entlastung der Einspritzleitung zum Verhindern des Nachspritzens allein. Die Entlastungsmenge beträgt dann im wesentlichen ein Entlastungsvolumen von Ventilhub x freier Ringfläche der Stirnseite des Entlastungsbundes 26. An der Drosselverbindung 27 fließen ferner bei der schnellen Hubbewegung des Ventilschließglieds keine wesentlichen Ausgleichsmengen vorbei, so daß die Förderleitung maximal entlastet wird. Aufgrund der großen Volumenentlastung ist der Restdruck in der Förderleitung 7' relativ gering, so daß die Druckwellen nur noch geringe Druckspitzen aufweisen, die in der Regel unterhalb des Öffnungsdruckes des Einspritzventils 8 liegen. Höhere Druckspitzen werden auch hier durch das Rückschlagventil 46 abgebaut. Statt mit einem Anschliff kann die Drosselverbindung 27 am Rücksaugbund auch mit Hilfe eines vergrößerten Spiels zwischen Bund 26 und Bohrung 24 oder durch Bohrungen im Bund selbst hergestellt werden.With larger fuel injection quantities and also with high delivery rates correspondingly high speed, the throttle influence of the throttle connection 27 increases in such a way that the suckback collar 26 emerges from the bore 24 and the delivered fuel can flow unthrottled past the suckback collar into the spring chamber 45. In this case, at the end of the delivery, the full valve closing member stroke is effective for sucking back fuel quantities. Here, the relief association essentially takes over the relief of the injection line to prevent post-injection alone. The amount of relief is then essentially a relief volume of the valve stroke x free ring area of the end face of the relief collar 26. Furthermore, during the rapid stroke movement of the valve closing member, no substantial compensation amounts flow past the throttle connection 27, so that the delivery line is maximally relieved. Due to the large volume relief, the residual pressure in the delivery line 7 'is relatively low, so that the pressure waves only have small pressure peaks, which are generally below the opening pressure of the injection valve 8. Higher pressure peaks are also reduced here by the check valve 46. Instead of using a bevel, the throttle connection 27 on the return suction collar can also be produced with the aid of an increased play between collar 26 and bore 24 or through bores in the collar itself.

Würde dann, wenn eine Brennkraftmaschine mit einer Leiselaufvorrichtung betrieben wird, der Bund 26 dicht in der Bohrung 24 geführt werden, so müßte das Schließglied 21 zunächst den vollen Hub, der dem Entlastungshub entspricht, ausführen; bis die Verbindung von der Förderleitung 7 zur Förderleitung 7' hergestellt ist. Es käme hier bei der geringen Förderrate zu einem verzögerten Einspritzpunkt. Weiterhin würde aber insbesondere beim Schließen des Schließgliedes die Förderleitung 7' in gleicher Weise entlastet, wie es bei Teillast oder Vollast bzw. bei hohen Förderraten der Fall ist. Diese Entlastung entspricht einem für eine geringe Förderrate beim Leerlaufbetrieb hohem Schluckvolumen, das erst aufgefüllt werden muß, bis in der Förderleitung 7' ein Druck erreicht wird, der dem Öffnungsdruck des Einspritzventils entspricht. Auch hier würde ein Spritzverzug eintreten und es wäre für den Pumpenkolben ein entsprechend langer Vorförderhub erforderlich. Dieser lange Vorförderhub, der aufgrund der durch die Leiselaufeinrichtung erreichten geringen Förderrate noch größer ist als bei Normalbetrieb ohne Leiselaufeinrichtung macht es erforderlich, daß bei der Einspritzpumpe ein relativ großer Nutzhub, dem Hub, der für die Kraftstofförderung zur Kraftstoffeinspritzdüse wirksam ist, zur Verfügung gestellt werden muß. Dieser Nutzhub für den Leerlauf geht andererseits dem Nutzhub im übrigen Lastbereich verloren. Dies erschwert in erheblichem Maße die Anwendung einer Leiselaufeinrichtung bzw. bedingt eine aufwendige Pumpenkonstruktion mit hohem Nutzhub.Would if an internal combustion engine is operated with a quiet running device, the collar 26 are guided tightly in the bore 24, the closing member 21 would first have to carry out the full stroke, which corresponds to the relief stroke; until the connection from the conveyor line 7 to the conveyor line 7 'is established. The low delivery rate would result in a delayed injection point. Furthermore, however, the delivery line 7 'would be relieved in particular in the same way as the closing member, as is the case with partial load or full load or with high delivery rates. This relief corresponds to a swallowing volume which is high for a low delivery rate during idling operation and which has to be filled up until a pressure is reached in the delivery line 7 'which corresponds to the opening pressure of the injection valve. A spray delay would also occur here and a correspondingly long pre-delivery stroke would be required for the pump piston. This long pre-delivery stroke, which due to the low delivery rate achieved by the silent running device is even greater than in normal operation without a silent running device, makes it necessary for the injection pump to provide a relatively large useful stroke, the stroke which is effective for fuel delivery to the fuel injection nozzle got to. On the other hand, this useful stroke for idling is lost to the useful stroke in the rest of the load range. This complicates the use of a silent running device to a considerable extent or requires a complex pump design with a high useful stroke.

Mit der hier vorgenommenen Ausgestaltung des Entlastungsbundes wird erreicht, daß bei kleinen Förderraten, insbesondere im Bereich des Leiselaufbetriebes die Förderleitung 7' nur gering entlastet wird. Da jedoch bei hohem Restdruckniveau auch in diesem Betriebsbereich Druckschwingungen in der Förderleitung 7' auftreten können, die dann über dem Öffnungsdruck des Einspritzventils 8 liegen, ist das Rückschlagventil 46 vorgesehen, über das in diesem Betriebsbereich die Druckspitzen abgebaut werden, indem Kraftstoff durch die Drossel 44 bei geöffnetem Rückschlagventil, dem Innenraum 36 und dem Entlastungskanal 35 über den Austritt 30 zum Pumpenarbeitsraum zurückströmen kann.With the configuration of the relief collar carried out here, the delivery line 7 'is relieved only slightly at low delivery rates, particularly in the area of quiet operation. However, since pressure fluctuations can also occur in the delivery line 7 ′ in this operating range at a high residual pressure level, which are then above the opening pressure of the injection valve 8, the check valve 46 is provided, via which the pressure peaks are reduced in this operating range by fuel being throttled by the throttle 44 when the check valve is open, the interior 36 and the relief channel 35 can flow back to the pump work space via the outlet 30.

Durch die Ausgestaltung der Drosselverbindung, die Bemessung des Entlastungsbundes bzw. Entlastungsvolumens und durch die Auslegung des Öffnungsdrucks des Rückschlagventils kann ein gewünschter Restdruck in den verschiedenen Betriebsbereichen der Brennkraftmaschine in der Förderleitung 7' aufrechterhalten werden, ohne daß der Öffnungsdruck der Einspritzdüsen nach deren Schließen überschritten wird. Der Öffnungsdruck des Rückschlagventils wird dabei in vorteilhafter Weise so gewählt, daß er etwa so groß wie der Einspritzventilschließdruck ist. Damit kann ein sehr hoher Standdruck oder Restdruck in der Förderleitung eingehalten werden bei geringstem Schluckvolumen. Entsprechend dem angepaßten Restdruck erhält man lange Spritzzeiten im Leerlauf-Leiselaufbetrieb, ohne daß diese so groß wären wie bei einem Druckventil, das kein Rückschlagventil aufweist. In diesem Fall würde wegen der Drosselverbindung 27 sehr hohe Restdrücke in der Förderleitungen 7' verbleiben und sich damit sehr lange Spritzzeiten einstellen, die zum Teil durch Nachspritzen noch verlängert werden.By designing the throttle connection, dimensioning the relief collar or relief volume and designing the opening pressure of the check valve, a desired residual pressure can be maintained in the various operating areas of the internal combustion engine in the delivery line 7 'without the opening pressure of the injection nozzles being exceeded after they are closed . The opening pressure of the check valve is advantageously chosen so that it is approximately as large as the injection valve closing pressure. This means that a very high stand pressure or residual pressure in the delivery line can be maintained with the lowest absorption volume. In accordance with the adjusted residual pressure, long spray times are obtained in idle-quiet operation, without these being as large as with a pressure valve which has no check valve. In this case, very high residual pressures would remain in the delivery lines 7 'because of the throttle connection 27 and thus very long spraying times would occur, some of which would be extended by post-spraying.

Claims (8)

1. Delivery valve for installation in a feed line (7, 7') between a pump working space of a fuel-injection pump and the injection point on the internal-combustion engine fed by the fuel-injection pump, with a valve-seat body (14) provided with a valve seat (19) and having a passage channel (24), in which is guided a delivery-valve closing member (21) which is arranged between the valve seat (19) and a compression spring (37) supported fixed in place in a spring space (45) and which has a sealing face (20) interacting with the valve seat (19), has a return-suction collar (26) located on the same side of the sealing face as the pump working space and inserted into the passage channel (24) when the delivery-valve closing member is in the closing position, and has a relief channel (28) which is provided with a throttle (44) and by means of which the passage channel (24) is connectable to the spring space (45) on the same side of the return-suction collar (26) as the pump working space, and which, on the same side of the throttle (44) as the pump working spsce, can be closed by means of a closing member (42) of a non-return valve (46) having a closing spring (40) supported on the valve-closing member, characterized in that the return-suction collar (26) is provided with a throttle connection (27) which connects the space adjacent to the return-suction collar on the same side as the sealing face to an adjacent part of the passage channel (24) leading unthrottled to the pump working space.
2. Delivery valve according to Claim 1, characterised in that the throttle connection (27) is formed from a flatened portion on the outside diameter of the return-suction collar (26).
3. Delivery valve according to Claim 1 or 2, characterized in that the delivery-valve closing member (21) has, on the same side as the spring space, an annular end face (32) with an axial stud (31) and a pot-shaped part (34) is attached to this annular end face by means of an outer collar (35), on which the compression spring (37) of the valve-closing member (21) rests, and in that an interior space (36) enclosed by the pot-shaped part is connected to the relief channel (28) and contains the non-return valve (46), the closing member (42) of which controls a throttle bore (44) leading through the wall of the pot-shaped part.
4. Delivery valve according to Claim 3, characterized in that the throttle bore (44) is arranged in the bottom of the pot-shaped part.
5. Delivery valve according to Claim 4, characterized in that the throttle bore (44) is widened in the form of a diffuser on the inner face of the bottom, forming a valve seat (43) of the closing member (42) of the non-return valve, the closing spring (40) of which is supported on the stud (31).
6. Delivery valve according to Claim 3, characterized in that the closing member of the non-return valve is a ball which is guided in a valve plate (41).
7. Delivery valve according to one of the preceding claims, characterized in that the delivery valve is used in a fuel-injection pump, the fuel-feed rate of which is reduced, in a specific operating range, as a result of the extraction of a part quantity of the quantity of fuel conveyed by the pump piston during its feed stroke.
8. Delivery valve according to one of claims 1 or 2, characterized in that the opening pressure of the non-return valve (46) is approximately equal to the closing pressure of the injection valve (3).
EP85104323A 1984-05-10 1985-04-10 Delivery valve Expired EP0163078B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19843417210 DE3417210A1 (en) 1984-05-10 1984-05-10 PRESSURE VALVE
DE3417210 1984-05-10

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EP0163078A1 EP0163078A1 (en) 1985-12-04
EP0163078B1 true EP0163078B1 (en) 1988-06-29

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US (1) US4648369A (en)
EP (1) EP0163078B1 (en)
JP (1) JPS60247049A (en)
KR (1) KR930010661B1 (en)
BR (1) BR8502199A (en)
DE (2) DE3417210A1 (en)
SU (1) SU1489583A3 (en)

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KR930010661B1 (en) 1993-11-05
BR8502199A (en) 1986-01-07
JPS60247049A (en) 1985-12-06
US4648369A (en) 1987-03-10
DE3563553D1 (en) 1988-08-04
EP0163078A1 (en) 1985-12-04
SU1489583A3 (en) 1989-06-23
DE3417210A1 (en) 1985-11-14
KR850008704A (en) 1985-12-21

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